The present invention generally relates to address signal reproducing systems in rotary recording medium reproducing apparatuses, and more particularly to a system capable of reproducing an address signal even during a random access operation or a high-speed search operation in which a reproducing element is forcibly shifted over tracks in the rotary recording medium reproducing apparatus.
A new information signal recording and/or reproducing system has been proposed in U.S. Pat. Nos. 4,315,283 and 4,322,836, of which the assignee is the same as that of the present application. According to this proposed system, the recording system forms pits in accordance with an information signal being recorded along a spiral track on a flat rotary recording medium (hereinafter simply referred to as a disc), without forming a groove therein. In the reproducing system, a reproducing stylus traces over along this track to reproduce the recorded information signal in response to variations in electrostatic capacitance.
In this system, since no grooves for guiding the reproducing stylus are provided on the disc, it becomes necessary to record pilot or reference signals on or in the vicinity of a track of a program information signal, on the disc. Upon reproduction, the reference signals are reproduced together with the program information signal. Tracking control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
By use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged since the recording track has no groove. The reproducing stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow-motion, or quick-motion reproduction becomes possible. Moreover, operations such as a random access, high-speed search, and automatic cueing operation in which the reproducing stylus is shifted to a position of a desired recorded program where the reproduction is to be started, can be performed with ease.
In order to perform operations such as the above random access, high-speed search, and automatic cueing operations, signals such as an address signal (hereinafter referred to as a chapter address signal) for indicating the number of the recorded program, and an address signal (hereinafter referred to as a time address signal) for indicating the position within the recorded program in reproducing time from the start of that recorded program or in reproducing time from the start of the first program recorded on the disc, are recorded onto the disc.
The above program information signal recorded onto the disc may be an audio signal, and the disc may be a digital audio disc onto which a PCM signal obtained by pulse-code-modulating the audio signal is recorded. For example, the PCM signal having a sampling frequency of 47.25 kHz is recorded in a time series manner in terms of blocks, wherein one block comprises one hundred and several tens of bits. The address signal is recorded in a time series manner in one bit at the last part of each block, to transmit all the one hundred and several tens of bits of the address signal by one hundred and several tens of blocks. This address signal having one hundred and several tens of bits is recorded twenty and some odd times for one revolution of the disc, and the content of the address signal is the same for the same track turn.
Conventionally, when performing operations such as the above random access, high-speed search, and automatic cueing operations with respect to a disc recorded with such an address signal, the address of the position where the reproducing stylus is reproducing and a desired address which has been set are compared. According to the difference between the two addresses, the reproducing stylus is moved at a high speed in a radial direction of the disc. If the address of the position of the reproducing stylus and the set address still differ after the reproducing stylus is moved, the reproducing stylus is again moved at a high speed in a similar manner so that the two addresses coincide.
However, in the conventional system, tracking control is not performed with respect to the reproducing stylus during the interval in which the reproducing stylus is moved at a high speed. Accordingly, not all the bits of the address signal can be reproduced during this interval, because the address signal is recorded in a scattered manner for each track turn. Thus, in the conventional system, there was a disadvantage in that the position of the reproducing stylus cannot be indicated by the chapter or the time during the above described operation. In addition, since the address signal is not reproduced during the interval in which the reproducing stylus is moved at a high speed, there was a disadvantage in that the reproducing stylus does not always and immediately reach the desired set address position by one high-speed moving operation.